Remove a null value from nested array of objects with conditions

I have a data like this:

[
    {
        "title": "Chemist I",
        "class_id": "CMT1",
        "deptcode": "001",
        "c_title_id": 978,
        "duties_details": [
            {
                "accmp": [
                    {
                        "d_c": "2021-11-17T14:43:22",
                        "date": "Nov 17, 2021",
                        "empid": 67,
                        "posdrid": 48,
                        "remarks": "Net",
                        "accomp_id": 46,
                        "month_year": "NOVEMBER , 2021",
                        "approved_by": null,
                        "date_created": "2021-11-14T14:43:00",
                        "pc_review_item_id": 2
                    }
                ],
                "prcnt": 15,
                "dscrptn": "Troubleshoot Computer",
                "pos_drid": 48
            },
            {
                "accmp": null,
                "prcnt": 10,
                "dscrptn": "Test CMT Data",
                "pos_drid": 49
            }
        ]
    }
],
[
    {
        "title": "Computer Programmer I",
        "class_id": "COMPRO1",
        "deptcode": "001",
        "c_title_id": 177,
        "duties_details": [
            {
                "accmp": [
                    {
                        "d_c": "2021-11-17T14:43:08",
                        "date": "Nov 17, 2021",
                        "empid": 67,
                        "posdrid": 40,
                        "remarks": "test",
                        "accomp_id": 45,
                        "month_year": "NOVEMBER , 2021",
                        "approved_by": null,
                        "date_created": "2021-11-15T14:43:00",
                        "pc_review_item_id": 1
                    }
                ],
                "prcnt": 30,
                "dscrptn": "Develop system procedures/methods/functions based on the system design and report to the immediate head once completed",
                "pos_drid": 40
            },
            {
                "accmp": null,
                "prcnt": 15,
                "dscrptn": "Write code for software patches and bug fixes",
                "pos_drid": 42
            },
            {
                "accmp": null,
                "prcnt": 15,
                "dscrptn": "Run series/level of software tests to spot and resolve logical(bug) & syntactical errors",
                "pos_drid": 41
            },
            {
                "accmp": null,
                "prcnt": 10,
                "dscrptn": "Write encountered/reported/spotted system issues/errors/bugs into the issue features of version control system",
                "pos_drid": 45
            },
            {
                "accmp": null,
                "prcnt": 10,
                "dscrptn": "Write documentations to the created system procedures/methods/functions",
                "pos_drid": 44
            },
            {
                "accmp": null,
                "prcnt": 10,
                "dscrptn": "Review created system procedures/methods/functions for system efficiency",
                "pos_drid": 43
            },
            {
                "accmp": null,
                "prcnt": 10,
                "dscrptn": "Commit and push every complete & working changes made to the source code into the version control system",
                "pos_drid": 46
            }
        ]
    }
]    

now based on the data, I want to remove the duties_details with a value of null from other positions but not in "class_id": "COMPRO1".

{
    "accmp": null,
    "prcnt": 10,
    "dscrptn": "Test CMT Data",
    "pos_drid": 49
}

I have tried like this but It returns undefined :

let filterDRData = DRData ? DRData.map((drdata) => {        
        if(drdata[0].class_id != "COMPRO1") {
            drdata[0].duties_details.map((dd) => {                
                return {
                    ...drdata,
                    duties_details:dd.filter(e => e.accmp == null)                      
                }
                    
            })
        }
    }):null

>Solution :

You outer lambda does not return anything.

this should work:

let filterDRData = DRData ? DRData.map((drdata) => {        
    if(drdata[0].class_id != "COMPRO1") {
        drdata[0].duties_details = drdata[0].duties_details.filter(e => e.accmp != null);
    }
    return drdata; // ADD THIS LINE
}):null